4io 
Horne and Williamson. — The Morphology and 
1,000 c.c. distilled water) + 10 c.c. N/5 NaOH diluted to 200 
c.c. with distilled water. pH 87. 
(b) 50 c.c. H3BO3, KCl + 25 c.c. N/5 NaOH diluted to 200 c.c. 
pH 9-3. 
(c) 50 c.c. H3BO3, KCl + 45 c.c. N/5 NaOH diluted to 200 c.c. 
pH 10. 
(d) Distilled water. 
B. A similar series in which the dilutions were made with neutralized 
potato extract instead of distilled water. 
(a) pH 8*5: (b) pH 8-9: (c) pH 9-8: (d) neutralized potato extract, 
pH 8. 
C. A similar series in which the dilutions were made with neutralized 
potato extract agar (1-5 per cent.). 
(a) pH 8 to 8-2: (b) pH 8*5: (c) pH 9*1 : (d) neutralized potato 
extract agar, pH 6 approximately. 
The pH values were obtained by the indicator method after the media 
had been autoclaved. Owing to the fact that the agar is coloured to a certain 
extent, the exact value was difficult to obtain in media containing agar. 
The media were made up in flasks containing 50 c.c. each, autoclaved, 
subsequently inoculated, using the three species of Eidamia , and kept at 
20° C. The results obtained are given below : 
Growth at 20° C. in boric acid buffer solutions and media containing boric 
acid buffer solutions , of different hydrogen-ion concentrations. 
Medium. 
pH. 
E. catenulata. 
E. viridescens. 
E. acremonioides. 
P.E. agar (C.d .) 
6 
moderate 
moderate 
moderate 
P.E. (B. d.) 
8 
numerous 
colonies 
solid gela¬ 
tinous mass 
scum-like 
growth 
P.E. agar with 
buffer (C. a.) 
8-8.2 
several 
colonies 
slight 
nil 
Various 
8-5-10 
nil 
nil 
nil 
N.B. At the end of 15 days the hydrogen-ion concentration of the liquid in neutralized potato 
extract containing E. catenulata was pH 8-2, of that containing E. viridescens pH 8-4, and of that 
containing E . acremonioides pH 7-6. 
Additional experiments were made with E. catenulata and E. viridescens 
using buffer solutions grading from pH 6*4 to 7*6, hydrogen-ion concentra¬ 
tions at which moderate growth occurs in other media (not containing boric 
acid), but the growth produced was of a feeble character in each case. 
A species of Aposphaeria , on the other hand, formed numerous well-defined 
colonies in boric acid buffer solutions, containing no other source of nutrient, 
ranging from pH 7-8 to pH 10, and Pleospora pomorum was capable of 
growth at pH 87. From these results it seems probable that the boric acid 
exerts an unfavourable effect on growth in so far as the species of Eidamia 
